Slab



H. H. BUNKER April 5, 1938.

SLAB

Filed oct. 9, 1955 2 Shets-Shegt 1 ATTORNEYS April 5, 1938. nH. H. BUNKER SLAB Filed Oct. 9, 1935 2 Sheets-Sheet 2 Patented Apr. 5, 1938 UNITED STATES PATENT OFFICE 4 Claims.

This invention relates to slabs and particularly to slabs for roadways on bridges and viaducts and for all structural uses in which it is desirable that the roadbed and road supporting structure be of minimum weight per unit area. Composite steel and concrete slabs have been used with success for bridge roadways owing to the facility afforded thereby in the building of a roadway and to the fact that no paving or road-surfacing other than that provided by the slabs is necessarily required. But to the extent that the usual forms of open grating have entered into the design of concrete slabs, concrete slabs so designed have failed to produce the economy in construction and the load carrying capacity per dead weight of slab as are desired, particularly for bridge roadways, and it is among the objects of my invention to provide a roadbed construction of metal and concrete having much less weight per 2'0 unit area and for a given strength than the filledin open mesh grating type of slab. To this end I use a metallic truss beam providing material in those portions of the slab where the stresses are greatest and in such quantity as to provide no more than the strength required wherebyl obtain a slab strong enough to meet given specications but lacking such weight as would otherwise be present on account of the use of excessive metal. There are also associated with the truss beams, and constituting therewith principal stress carrying elements, a number of cross bars which are so related to the truss beams that, in addition to serving as separators for the truss beams and as load-distributing members, function to prevent deflection of the upper and lower chords of the truss beams in vertical and lateral directions.

It is therefore among the objects of my invention to provide a metallic skeleton for concrete-lled slabs so constructed as to provide a relatively strong slab for the amount of metal entering into its construction.

Further and other objects of the present invention will be hereinafter set forth in the accompanying specification and claims and demonstrated by the drawings which show by way of illustration a preferred embodiment and the principle of my invention, and what I now consider the best mode in which I have contemplated applying that principle. Other embodiments of the invention employing the same principle may be used and structural changes made as desired by those skilled in the art within the spirit of the appended claims without departing from the present invention.

In the drawings: v

Fig. 1 is a plan view of a filled slab with portions thereof broken away.

Fig. 2 is a longitudinal section on line 2-2 of Fig. 1.

` Fig. 3 is a transverse section on line 3-3 of Fig. 1.

Fig. 4 is a perspective View of the slab partly filled with cementitious material.

Fig. 5 is a View illustrating the manner of assembling the longitudinal and transverse members. f

Fig. 6 is a section on line 6-6 of Fig. 5.

Fig. 7 is a sectional view similar to Fig. 6, with the members engaged as in use. l

Fig. 8 illustrates a modiedform of slab with a form plate suspended therebelow.

Fig. 9 is a section on line 9-9 of Fig. 8.

Fig. 10 is a plan showing abutment of two slabs along their longitudinal contacting edges and an arrangement for connecting such slabs together across their line of separation.

' Fig. l1 is. a section on line II-Il of Fig. 10.

' Fig. 12 is a section on line l2-l2 of Fig. 10.

Having reference to the drawings, the essential load carrying members of the slab are in the form of 'a metallic frame-or skeleton consisting of longitudinally 'and transversely extending members. As indicated hereinabove, it is of particular importance that the weight of slabs, such as are used for roadways, be maintained at a minimum for a given strength. Slabs for roadways are frequently made of steel and concrete, and it is desirable that the amount of steel used be maintained at a minimum so as not to provide a slab of excessive weight.

The metallic frame or skeleton of my invention includes longitudinal members or truss. beams I0 having upper and lower chords Il, l2, with anges, and an open-work web i3 providing trusslike members extending between the upper and lower chords. I have chosen to illustrate truss beams I0 in the form of I-beams having symmetrical chords and flange portions, but beams having flanges of different shapes, weights and widths at their top and bottom chords may be used. The shape of the openings in the webs of the truss beams is determined by the slope and conguration of the truss members extending between the chords but must be of such dimensions as will accommodate the maximum height of the cross bars. In assembling, the cross bars are passed through the series of truss beams which are to constitute a iinished frame.

Each cross bar is notched as at I5, i6, to acterial of the cross bars may-be made to bite into commodate and engage the upper and lower cho-rds of the truss beams. To make certain that the cross bars will contribute to the Vertical and lateral support of the upper and lower chords of the truss beams, all surfaces of a notch should contact with its associated chord and the notches are so designed that they will accomplish this and be tightly engaged .at their bottom portions with the inner edges of the chords. The proportions should preferably be such that when each cross bar is passed through aligned openings in the webs of the truss beams and turned angularly, the vertical portions I1, I8 of the chords of the truss beams will be forced to the full depth of their respective notches I and II-` lower chords, as indicated at 20,' 2I, Fig; 5. After all of the cross bars have been positioned vertically, the bulging portions of the truss beams may be returned to normal by passing the slab under a press. This manner of constructing the metallic skeleton is desirable because it ensures the obtaining of .a tight vertical contact with the upper and lower chords.

'I'his method of locking the upper and lower chords to the cross bars also' alfords .a meansof obtaining dove-tail connections -between the cross bars and the chords of the truss beams, as shown in Fig. '7, if such is desired. The compression of the chords of the truss beams towards each other in a press causes metal of the truss beams to flowl into the dove-talslots in the cross bars. While the use of dove-tail connections between the slots I5 and I 6 and chord elements I'I and I8, respectively, is not indispensable, the rigidity of the skeleton may be improved by utilizing dove-tail connections at either the upperk or lower bottom chord orat both chords. Without the dove-tails a secure connection may be had because the mathe chords of the truss beams which may be comparatively softer than the cross bars. The rmer the engagement between the cross bars and truss beams, the more accurately the truss beams will be held in alinement and the more certain it is that the upper and lower chords of the truss beams be prevented from buckling or twisting under load.

One advantage of my inventionis that adjacent slabs may be rigidly connected together along their abutting longitudinal edges, as illustrated in Figs. 10 and 11. In these figures, adjacent slabs 22, 23 abut on line 24,` and in the absence of supporting structure passing between these two slabs, neither one of the slabs will provide support for a load carried by the other slab. The construction of my slab enables the use of an auxiliary cross bar 25 adapted to be placed alongside of a regular cross bar I4 and extend across the parting line 24 of the adjacent slabs, or, if desired, every fifth or tenth regular cross bar may.

be omitted from placement inthe skeleton until the skeleton is laid, and then be so placed as to cross the parting line. bar will lock the adjacent slabs together and tend to prevent unequal deflection between adjacent slabs.

W'hen the skeleton is to be used as a slabfor a roadbed, it is filled with concrete or otherflling-in material 26, and in order to support this material when being poured, strips of sheet metal 21 constituting forms may be availed of between the truss beams. These strips are preferably positioned-before the cross ybars are :turned-tof their The overlapping. crossnormal positions so that they may be held in place by the pressure of the cross bars against their upper surfaces. 'Ihe strips are thereby held firmly in place upon the upper surfaces of the lower flanges of the truss beams.

In some districts it is not permissible to leave exposed the steel underside of a slab, and in order to meet regulations of this sort the lower chords of the truss beams must be covered with concrete. The design of my slab is well suited for this purpose because it provides a means for fastening hangers 30 whereby a supporting plate or form 3| may be suspended. These hangers may take any suitable form having lips 32, 33, supported upon the lower anges of adjacent truss beams and held in place by the wedging action of the cross'bars I4 which bear upon their upper surfaces. The'form plate 3| may be afxed to the hangers as is customary in the trade, as by bolts-34':

While I have illustratedimy slabas being iilled with concreteup to'the upper. surfaces ofthe truss beams Ill, it is. tobe understood. that the concretemay extend` above these surfaces and also that the portions .3T-of the cross bars I4inmum dimension ofthe openings 36 in the websf ofthe` truss beams.

While the truss-like members constituting the webof the trussbeam may be built up from individual pieces, I preferably employ a truss beam formedin one piece. This type of construction may be obtained from.a rolled.I.-bearn suitably punched or out and expanded to cause openings in its web ofthe desired conguration.

It will be observed that the mesh or open-work nature of the webs of the truss beams affords opportunity for the material,r such as concrete, to be thoroughly distributed throughout the slab, and morder to facilitate further -distribution of the filling material, I`have provided holes 38. in the Ycross bars. These holesare so locatedA that the loss of material from the cross bars does notV sacrifice needed strength.

A desirable feature of my invention is that no welding, riveting or other meansof fastening for holding the truss beams and cross bars to gether is-necessary owing to the manner of assembling. suchrmembers, and this is particularlyr The'skeleton is-suitab1e for use as a floor or' support for flooringv and as such the use of concrete or other filling materialembedding the truss-v beams is optional.

I claim:

1. A roadbed comprising a plurality of composite metal and concrete slabs, each slab having a metallic skeleton including spaced longitudinally extending beams having upper and lower chords and diagonally extending truss-like elements connecting the upper and lower cho-rds and leaving openings therebetween; cross-bars in the form of vertically disposed strips extending laterally to said beams and through aligned openings in said beams, said cross-bars being notched for engaging the upper and lower chords of the beams to provide support therefor; and other cross-bars similar to said rst mentioned laterally extending cross-bars and arranged in staggered relation thereto across the slabs soI as to extend beyond the longitudinal edge of one slab and into the adjacent slab, said other crossbars being in locking engagement with at least the outside longitudinally extending beam of the adjacent slab into which they extend so as to constitute adjacent slabs of the roadbed into one substantially rigid slab construction free from apparent deflection between the metallic skeletons of the individual slabs when in use.

2. A skeletonfor a slab comprising spaced longitudinally extending I-beams with their webs disposed in vertical planes, the webs having aligned openings therein leaving upper and lower chords connected b-y diagonally extending trusslike elements in the webs of said beams; crossbars extending laterally to said beams and through aligned openings in the webs of said beams, said cross-bars being provided with notches for engaging the beams, the configuration of said notches and the spacing between upper and lower notches being such as to cause each cross-bar to act as a vertical strut between the upper and lower chords of the I-beams; a forming plate below said I-beams and means suspended from the lower anges of the I-beams for supporting said forming plate, said means being supported upon the lower flanges of said I-beams and maintained in engagement therewith by the lower edges of said cross-bars.

3. A metallic structure comprising a plurality of beams spaced from each other and in parallel arrangement, said beams having openings through their webs which are aligned laterally of the structure; cross-bars extending laterally to said beams and through aligned openings in said beams, said cross-bars serving to unite said beams in interlocking relationship and into a unitary metallic skeleton unit forming one o-f several units of a fabricated structure,'said cross-bars having notches in their upper and lower edges in engagement with the upper and lower chords of the beams of a unit off the fabricated structure, and additional cross-bars overlapping the ends of said iirst named cross-bars and extending across the parting line of adjacent units of the fabricated structure and into said adjacent units, said last named cross-bars also having notches in their upper and lower edges cooperating with the upper and lower chords of beams of adjacent units whereby relative deflection between adjacent units of the structure is prevented and the adjacent units are maintained in locked relation in respect to each other.

4. A metallic skeleton structure comprising a plurality of beams spaced from each other in parallel arrangement, said beams having upper and lower flanges and open webs formed by openings in their webs which are of less height than the height of the webs thereby providing parallel sided web portions below the upper flanges and above the lower flanges; and cross-bars extending laterally to said beams and in supporting relation to their upper and lower chords, said cross-bars extending through Valigned openings in the webs of adjacent beams and having notches in their upper and lower edges in engagement with the upper and lower chords of the beams, said notches having oppositely facing vertical edges engaging the parallel sides of the web portions o-f the beams below the upper flanges and above the lower flanges of the beams and having dove-tail interlocking relationship between the bottoms of the notches and the engaging web portions of the beams, whereby the beams and the cross-b-ars are firmly secured together at the intersections of the chords and cross-bars.

HERBERT H. BUNKER. 

